This invention relates generally to heat packs, and more particularly to a face or body mask characterized as containing a supercooled salt solution that controllably crystallizes to produce heat.
Heat packs incorporating unusually advantageous trigger constructions are described in our U.S. patent application Ser. Nos. 177,258 and 565,699. There is need for a heat pack construction and method of use adapting it to face masks, and other body mask uses.